Reproduction method



Oct. 16, 1945. R. F4LEDOUX 2,386,806

REPRODUCTION METHOD Filed Oct. 1, 1942 EDEEET F.LEDDUX,

Patented Oct. 16, 1945 UNITED sures; PATENT OFFICE I narnnmnrxon I V Robert F. Ledoux, Springfleld, Musa pp ca on1 :ml ,(cl .ra;e)l No.460,346

(Grmted under the act of Marc]! 3, ns, au amended April 30, 1928: 370 O. G. 757) Inspection et nearly al] small manufactured[ components by the use of gauges-is not aitogether satisfactory because of the small size and odd shape of certain components. Even with sau8es it is oftentimes diflicult for the inspector to determine whether the component conforms to required dimensions. Furthermore sauge inspectian neCessarily checks only the most significant dimensions. Another drawback to the inspection of small components by the use of gauge is the high cost of these gauges.

A highly satisfactory method for checking any such small component without the use of gauges has however been evolved. This method consists of comparing an enlarged carefully drawn contour lay-out of the component with a proJected image of the component enlarged to the same scale. In this manner the component can be readily checked with a master lay-out to determine whether any discrepancies exist in the manufactured component by direct comparison. As both the lay-out and the projected image are produced at a greatly eniarged scale the comparison can be rapidly made with a high degree of accuracy.

This procedure is conveniently accomplished on a projection comparator, When the component is placed on the comparator the image of the component may be projected onto the screen of the comparator to any desired enlargement. However, when comparing the component with the contour lay-out the image of the component must be projected onto the screen at exactly the same scale as that of the contour lay-out. The lay-out is then placed over the image of the component and the contour et the projected image comparedwlth the lay-out. It is thus readily seen that a very accurate comparison can be made.

' The main drawback with this procedure however has been that the medium on which the contour lay-outs are drawn is subject to dimensional changes due to humidity and temperature variations et the atmosphere. It is readily apparent that any slight dimensional change of the contour lay-out due to shrlnkage or expansion of the inedium on which the la-out is made results in distortionof the true drawing and a.

comparison with the component will be worthess.

Accordingly it is an object of this invention to provide a method for reproduction of accurately drawn contour lay-outs oi small components that is not subject to dimensionai changes due to variations in atmospheric conditions.

'Ihe speciflc nature of the invention as well as other chicots and advantages' thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawing in which:

Fig. 1 is a front elevationai view of a projection comparator showing the enlarged image 01 a component on the viewing screen of such comparator and the master contour on a glass plate superimp0sed on such image.

Fig. 2 is a perspective view showing the viewing screen of a comparator with an eniarged image of a component thereon and a, glass plate,

having a master contour theieon of the same size as the enlarged image, about to be superimposed on such image for comparison of the enlarged contour et the component with the master contour.

- Another object of this invention is to provide a contour reproduction medium that is convenient and inexpensive to use.

In the past contour lay-out drawings have been made on tracin cloth. When subJected to much handling these tracings quickly becam e soiled and were soon unflt for use. Furthermore tracing cloth is greatly affected by variations in atmospheric conditions and is therefore subject to dimensional changes. It is well known that reproduction et drawings can be readily and conveniently rep roduced by the medium of photography. Accordingly a direct contact print from a contour lay-out tracing (not shown) was made on a sensitized glass photographie plate. A glass plate was used instead et photographie film because the latter is subject to dimensional changes due to varying atmospheric conditions whereas the former is relatively unaflected.

From the negativa thus made a direct positive contact plate l is made. Such plate is then placed on a. screen 2 as shown in Figs. 1 and 2 ci a projection comparator 3 and compared with a projected image 4 as shown in Figs. 1 and 2 of a component 5. Repeated trials and careful scientiflc measurements under greatly varying conditions of temperature and humidity indicate that the reproduction o! thee contour iay-outa on photographie (lue plates 13 hizhly aatieflctory becaueetbe dimension! ohms otthiamatefla} axeeoamallth&ttbeycanbeaflbignod. It iaimportanthowertbatwhexbflanative be mnde fion: the contour inyout tracinz veryebortiyatrtbetrinxiecnflcdd beiore thetrtcingchans dimemionafly;

11mn it in readfly apparent that accurate reproduction of contour lnwout drawinu can be neadily made on -photoflnphic clou pintes and tint theee plates have no appreciable dimensions! change; reurdieee of atmospheric conditions. A furtber advantase of this proceu is foimd in the eue, convenienee and low ooct with which duplient: positive plates are made. In the event thntanyottbepiflmm deetroyedtnother maybereadflymadefmtbemrnaflnon procedureotmakinaanewconwmnt drawinz I enfin: 'Ihe mcthod of optical contour comparieon consisting of, producing trom a contour iayout drawingadirectcontactpflntonamfldflwtographie medium which in noi; tubJect to dimeneional chanee, matin: from the necative thue' produced a direct positive contact prodiflon on t transparent elles plate, projectim on a ecreeu a lizht imaxederid from the contour to betcated,endthenphflnzsflidlh plateover nid image no as to compare the photographie reproduction therewitb.

ROBERT 1". LIDOUX. 

